THE rarest Gamecube game?

[Mayhem]

Here's the cover of the Walmart Exclusive NASCAR 2005, assuming I can do this right...

I'd love to know what's different as it looks completely identical to the copy I own. Bar the sticker on the manual starting "Walmart exclusive".

[Kitsune Sniper]

Stu already said what's different - the sticker with a code to unlock a new racetrack.

I've seen a lot of "Walmart exclusive" games where the only difference is a code to get an item... you can eventually unlock.